n.
willingness or readiness to receive (especially impressions or ideas); "he was testing the government's receptiveness to reform"; "this receptiveness is the key feature in oestral behavior, enabling natural mating to occur"; "their receptivity to the proposal"

n.
a rule or law concerning a natural phenomenon or the function of a complex system; "the principle of the conservation of mass"; "the principle of jet propulsion"; "the right-hand rule for inductive fields"